1. Field of the Invention
The present invention relates generally to backlight modules, and more particularly to a polarization splitter backlight module for converting a non-polarized light beam into a single polarization state.
2. Description of the Related Art
With the advent of the information technology (IT) age, there is an increasing demand for high-quality electro-optical displays (LCDs). Higher quality imaging requires the more efficient utilization of light sources. Conventionally, for obtaining single-polarized light beam output form a LCD backlight plate, a polarization plate is arranged near the light source to inhibit the passage of certain polarized light beams, whereby the polarized light beams which are not parallel are prevented form being transmitted. In practice, the resultant light beams of a single polarization state are less than half of those of the original light source in terms of illuminance.
With reference to FIG. 1, a conventional liquid crystal display comprises a non-polarized light source 30, a diffusion plate module 20, a polarization plate 14 and a liquid crystal component 50. Light beams emitted from the non-polarized light source 30 are introduced into the diffusion plate module 20, and are polarized by the polarization plate 14 so as to be utilized by the liquid crystal component 50. The intensity of the resultant light beams will be reduced over 50% and will be less than half of the intensity of the original light beam due to the screening effect through the polarization plate 14. Since the optical energy loss between the resultant and original light beams is considerable, the power consumption of a system using such a construction is very significant, thereby limiting the quality of the image display.
In view of the above problems, the object of the present invention is to provide a polarization splitting backlight module for generating a light source of a single polarization state, which reduces the optical loss in light beam output, is suitable for mass production, and decreases manufacturing costs.
Another object of the present invention is to provide a polarization splitting backlight module, which is easily integrated with conventional light guides and achieves high-quality polarization splitting.
To achieve the above objects, the polarization splitting backlight module according to the present invention for generating a light source of a single polarization state comprises:
an under plate having an upper surface and a ridged lower surface;
a phase retardation reflection film of high reflectivity, provided on the lower surface of the under plate;
a substrate having a lower surface, substantially complementary to the upper surface of the under plate, and an upper surface;
a scattering structure provided between the substrate and the under plate for altering the polarization state and the travelling direction of the light beam; and
a polarization splitting film provided on the upper surface of the substrate, which allows the light beams of different polarization states to be transmitted or reflected.
In order to enhance the optical performance, the ridge pitch of ridged surface of the under plate may be constant or not so as to increase the design freedom. Moreover, in order to increase the efficiency for altering the polarization states, the phase retardation reflection film is utilized. In addition, four lateral sides of the polarization splitting backlight module may be optionally coated with a reflection film, so as to increase the transmission efficiency of the light beams.
Furthermore, the polarization splitting backlight module according to the present invention can be easily integrated with a conventional liquid crystal display backlight module. This is achieved by attaching the polarization splitting film and the upper surface of the under plate according to the present invention to the upper side and lower side of the diffusion plate of the conventional backlight module respectively.
Additional advantages, objects and features of the present invention will become more apparent from the description which follows.